Hardening of photographic sttver



Patented Jan. 10, 1950 UNlTED STATE-Sf PATENT OFFICE,-

'' HARDENING, or rnoroeimemo SILVER HALIDE" GELATIN EMULSIONS WITH NITRO .ALooHoEs Bernard A. Orkin, Woodbury, N.. .I'.,. assignor to General Aniline & Film Corporation, N ew- York,-

N. Y., a corporation of Delaware No Drawing. Application December 1-0, 1946-,

' Serial No. 715,351

4 Claims (01. 95-7) 1 a 2 invention relates to photographic gelatin: The foregoing objects are accomplished, ac-- and more particularly to the hardening of photocording-to the present invention, by incorporatinggraphic gelatin and gelatino silver halideemulin the gelatin or gelatinosilver-halide emulsion, a,

sions to yield compositions having: an appreciable primary aliphatic nitro alcohol of not more than increase melting point good stability on" ficarbon atoms; with or'withou-t other compounds ageing with respect to fog, speed, and gradation. which alone possess little or nohardening effect IIEn the preparation of: photographic gelatin disupon gelatin or gelatino silver-halide emulsions, persions and gelatino silver-halide emulsions, it u n" o ju i h" the nitrO alcohol 910061- has been the practice to treat the dispersions and e et th h d i action h e elimination emulsions, prior to coating, with a hardening h af a and also inhibit the agent so as toreduce the-tendency of the gelatin derlcy of the photograp m t to f O to soften, or to distend during processing of the fi photo'graphic material containing the gelatin, As ampl s of su ta p ima a p i i particularly at-temperatures higherthan the tem alcohols of notmore than 6 carbon atoms, the perature specified for processing' the particular 5 follOWing are illustrative photographic material. Compounds which have g H been used for hardening gelatin as such or in silver-halide emulsions are formaldehyde, hy- HOCH2 CH20H droxy aldehydes, acrolein, glyoxal, and derivatives N02 thereof, and mixtures oi an aliphatic aldehyde 9!- -ni ,3 p p 0 with an aromatic compound containing at least CH '5 one nuclear hydroxy substituent group such as phenol, resorcinol, resorcyclic aldehyde, and the I cflnrfiyflcmoiH like: Although formaldehyde and hydroxy alde- N02 hydes are satisfactoryas hardening agents, these 5': I 2.methy1: 2 nitm.1.propan01 compounds possess the undesirable property 0t i producing excessive fog, desensitization, or flat- $2135 toning of. gradation in the processed film. Any noom-o-omon hardeners thatfunction by the liberation. of N formaldehyde will. also have these deleterious eliects as well. as thatof "after'-hardening.- z'etlhym'mtmlgpmpanedufl Aliphatic aldehydes, with an aromatic compound I onion containing at least one nuclear hydroxy substi- I H0CH2CNO2. tuent group, 1nduce some increase in the melting point. They fail, however, to give. both an ape OHZQH preciable increase in the melting point and g0o d Tnsqm'dmxymethyl)mtmmethane stability upon ageing in respect to fog, speed, and l jg cmcncmog gradation. Q It isan object of the present invention. to pro- I t 2 vide a photographic gelatin or a gelatino silver- 2'mtro'l'butanol al d emulsion having an appreciable higher. The compounds which alone possess little melting point and much better stability on ag'e-. 013110 hardening effect on gelatin or gelatino' m than gelatin or gelatin) silver-halide emu}; silver-halide emulsions, and which may be added: PP Per V I, I in conjunction with the nitro alcohol, are 2,l di f .Another obiect is to provide gelatin-layers and '45s" hydrpxy benzaldehyde (resorcylic aldehyde)" and gel'atino silver-halide emulsion layers in which the I 1,3 b dio1- (res r inol) The function of gelatin is not subject to the phenomenon known; 2 4; y be'nzaldehyde in the mixture is as after-hardening. boost or accelerate the hardening action of the A f r her Object i to provid a el tino si1ver-' nitro alcohol. When resorcinol is added to this halide emulsion which will not fog on storage. at! ombination, the optimum in hardening as well A still further object is to plQvide a gelatino as inphotographicproperties obtained. Avery; silver -halide emulsion wi l'l'be resistant' to desirable increase in melting point of gelatin or relatively high. processing temperatures witho gllaj tinosilver halide' emulsions is obtained bv fogging; loss of speed, and'lossof gradation. the-{utilization of" nitrofalcohols alone, said in -('Jther objects will appear hereinafter. crease'in melting point being'unaccompa-niedby any tendency for the gelatin or emulsion to undergo the phenomenon of after-hardening. It has been found that the nitro alcohols depress the speed and gradation of the photographic emulsions a slight amount. Such losses, however, are more than compensated for by the valuable contributions made by the use of the nitro alcohols. Furthermore, if with the nitro alcohols there be added 2,4-dihydroxy benzaldehyde, greater hardness is obtained, the ZAL-dihydroxyv benzaldehyde operating as it were to accelerate the hardness attributable to the nitro alcohols. The 2,4-dihydroxy benzaldehyde in addition has the valuable property of reducing the losses in speed and gradation which accompany the use of the nitro alcohols. The results obtained with the nitro alcohols in admixture with the 2,4-dihydroxy benzaldehyde are greatly improved if there also be employed resorcinol. This compound does not detract in the slightest from the hardening effect obtained with the other components and rather surprisingly in cooperation with said other ingredients confers upon the final sensitized emulsions a very excellent stability on ageing with respect to fog, speed and gradation. While, therefore, the invention contemplates the utilization of the nitro alcohols alone to'effect hardening while avoiding the phenomenon of afterhardening," it likewise contemplates the employment with the nitro alcohols of 2,4-dihydroxy benzaldehyde and resorcinol either alone or together. Inasmuch as best results are obtained when all three components are employed, the use of the same represents the preferred embodiment of the invention.

It is to be noted that from the large class of dihydroxy benzaldehydes, 2,4-dihydroxy benzaldehyde is the only one to accelerate the hardening effect of the nitro alcohol without impairing the photographic characteristics of the emulsions, and from the large class of aromatic hydroxy compounds containing at least 1 nuclear hydroxy group, resorcinol was found to be the only one, when in an admixture with a nitro alcohol and 2.4-dihydroxy benzaldehyde, to act as a stabilizing agent so as to impart excellent stability to the emulsion with respect to fog, speed, and gradation.

Where it is desired to increase the melting point of the gelatin in a gelatin dispersion utilized in the preparation of non-curling layers, filter and anti-halation layers, or anti-abrasion layers, a sufficient quantity of the nitro alcohol alone is added. While the exact amount of the nitro alcohol may be varied within wide limits and with due regard to the particular type of gelatin dispersion employed, in general, amounts ranging from 0.05% to 2.5% based on the dry weight of gelatin in the dispersion are preferred. In these amounts, effective hardening is obtained without after-hardening, i. e., the melting point of the gelatin does not vary with time or with long periods of storage prior to actual use and processing of the photographic material provided with such a layer.

In cases, especially in anti-abrasion layers, where the optimum in hardness is desired, a mixture of the nitro alcohol and 2,4-dihydroxy benzaldehyde is employed. The amount of 2,4-dihydroxy benzaldehyde, to be added to the preceding amounts of the nitro alcohol, may vary from 0.005% to 2.5%based on the dry weight of gelatin- -m" hardening gelatin emulsions}. which are. slightly alkaline, i. e., emulsions having a pa greater than 7, generally between 7 and .5 t he exact amounts of the nitro alcohol, 2,4-dihydroxy benzaldehyde, and recorcinol may also be varied within wide limits depending largely upon the desired degree of hardening, stabilizing effect, and gradation. In general, the amounts of' the nitro alcohol may vary from 1 to 5 parts by weight, the amount of 2,4-dihydroxy benzaldehyde may vary ,from 0.1 to 5 parts by weight, and the amount of resorcinol may vary from 1 to 10 parts by weight per 10 kilogram of emulsion containing 23-10% gelatin.

Where it is desired to increase the speed and gradation of a silver-halide emulsion, I prefer to use lresorcinol in conjunction with the nitro alcohol and 2,4-dihydroxy benzaldehyde. It is to be understood, however, that these emulsions may also be hardened by mixing therewith prior to coating the nitro alcohol alone or in combination with 2,4-dihydroxy benzaldehyde. In the latter case the melting point of the gelatin rises appreciably without the attendant serious loss of photographic characteristics.

While the following examples describe in detail the methods for accomplishing the afore: stated objects, it is to be understood that'they are given merely for the purpose of illustration and are not to be construed as limiting the scope of the invention.

EXAIWPLE I EXAMPLE II Twenty mls. of a 5% aqueous solution of 2- ethyl-2-nitro-1,3-propanediol and 80 mls. of a 5% aqueous solution of 2,4-dihydroxy benzaldehyde were added to 10 kilograms of a photographic silver-halide emulsion, containing 840%- gelatin and melting at 0., at a temperature of 40 C. A glass plate was coated with a thin layer of this emulsion and dried at room temperature. The emulsion layer melted at 47 0., and the film was tougher than the film of Example I.

EXAMPLE III This example graphically illustrates the results of incorporating tris-(hydroxymethyl) nitromethane, 2,4-,-dihydroxy benzaldehyde and resor cinol in an X-ray emulsion containing 840% j gelatin whereby not only the melting point of the gelatin is increased but excellent photographic properties are obtained. All the parts are in per cent by weight based on the weight of the emulsion.

X-ra'y' emulsion Quantity oi Tris-(hydroxymetliyDmitromethane. 0. 023 Quantity of 2, -Dihydrow-benzaldehyde 0 0. 03 Quantity'of Besorcinol 0 O. 07 M. P.,G.; 47 Fog 0. 16 Speed '196 Gradation O.

EXAMPLE IV This example shows the effect. of fog jin a silverhalide emulsion containing .8-10%..igelatin'.by a; j mixturefot 2-nitro-1,3j-propanedio1, 2,4 dihydroxy' j 18 benzaldehyde, and resorcinol. All parts are in" per cent based on the dry weight of the gelatin in the emulsion.

2-Nitro-1,3- 2,4-Dih ydroxy Resor- Fog propanediol benzaldehyde cinol Value 0 O 0 0. 20 0. 1 O. 2 0. 3 0. l6 0. 2 0. 2 0. 8 0. 16 0. 2 (l, 4 0v 6 0. 14 0.2 0.12 0. 48 0.12 0. 2 0. 24 0. 36 0. 10

From the foregoing examples, it is clearly apparent that my invention is not only applicable to the preparation of photographic silver-halide emulsions of satisfactory hardening properties, but also to the preparation of gelatin dispersions and dispersions of gelatin substitutes, which are normally capable of being hardened with formaldehyde, especially those which are and have been used in the preparation of various coatings or layers on paper, cloth, film, glass, and other surfaces.

I claim:

1. A photo-sensitive element containing a photographic gelatino silver-halide emulsion layer hardened by means of a primary aliphatic nitro alcohol of 3 to 6 carbon atoms, 2,4-dihydroxy benzaldehyde, and resorcinol.

2. A photo-sensitive element containing a photographic gelatino silver-halide emulsion layer hardened by means of tris-(hydroxymethyl) -nitromethane, 2,4-dihydroxy benzaldehyde, and resorcinol.

3. A photo-sensitive element containing a photographic gelatino silver-halide emulsion layer hardened by means of 2-ethyl-2-nitro-1,3-propanediol, 2,4-dihydroxy benzaldehyde, and resorcinol.

4. A photo-sensitive element containing a photographic gelatino silver-halide emulsion layer hardened by means of 2-nitro-1,3-propanediol, ZA-dihydroxy benzaldehyde, and resorcinol.

BERNARD A. ORKIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,165,421 Sheppard et al. July 11, 1939 2,206,819 Martin July 2, 1940 2,426,128 Trowell -1 Aug. 19, 1947 

1. A PHOTO-SENSITIVE ELEMENT CONTAINING A PHOTOGRAPHIC GELATINO SILVER-HALIDE EMULSION LAYER HARDENED BY MEANS OF A PRIMARY ALIPHATIC NITRO ALCOHOL OF 3 TO 6 CARBON ATOMS, 2,4-DIHYDROXY BENZALDEHYDE, AND RESORCINOL. 